Aqueous Resin Composition for Abrasive Articles and Resulting Articles

ABSTRACT

An aqueous polymer binder composition adapted for the manufacture of abrasive articles, such as coated abrasive articles, comprising at least one saccharide, at least one polycarboxylic organic acid, and at least one crosslinking catalyst. The aqueous composition is formaldehyde-free and can further comprise rheology modifiers, fillers, and hydrophobizing agents.

FIELD OF THE DISCLOSURE

The present invention relates to an aqueous resin binder composition,abrasive articles including the same, and methods of making and usingthe aqueous resin binder composition and abrasive articles.

BACKGROUND

Abrasive articles, such as coated abrasive articles, are used in variousindustries to abrade work pieces by hand or by machine processes, suchas by lapping, grinding, or polishing. Machining utilizing abrasivearticles spans a wide industrial and consumer scope from opticsindustries, automotive paint repair industries, and metal fabricationindustries to construction and carpentry. Machining, such as by hand orwith use of commonly available tools such as orbital polishers (bothrandom and fixed axis), and belt and vibratory sanders, is also commonlydone by consumers in household applications. In each of these examples,abrasives are used to remove surface material and affect the surfacecharacteristics (e.g., planarity, surface roughness, gloss) of theabraded surface. Additionally, various types of automated processingsystems have been developed to abrasively process articles of variouscompositions and configurations.

Surface characteristics include, among others, shine, texture, gloss,surface roughness, and uniformity. In particular, surfacecharacteristics, such as roughness and gloss, are measured to determinequality. Typically, defects in a surface are removed by first sandingwith a coarse grain abrasive, followed by subsequently sanding withprogressively finer grain abrasives, and even buffing with wool or foampads until a desired smoothness is achieved. Hence, the properties ofthe abrasive article used will generally influence the surface quality.

In addition to surface characteristics, users are sensitive to costrelated to abrasive operations. Factors influencing operational costsinclude the speed at which a surface can be prepared and the cost of thematerials used to prepare that surface. Typically, a user seeks costeffective materials having high material removal rates.

However, abrasives that exhibit high removal rates often exhibit poorperformance in achieving desirable surface characteristics. Conversely,abrasives that produce desirable surface characteristics often have lowmaterial removal rates. For this reason, preparation of a surface isoften a multi-step process using various grades of abrasive. Typically,surface flaws (e.g., scratches) introduced by one step are repaired(e.g., removed) using progressively finer grain abrasives in one or moresubsequent steps. Therefore, abrasives that introduce scratches andsurface flaws result in increased time, effort, and expenditure ofmaterials in subsequent processing steps and an overall increase intotal processing costs.

In an effort to achieve certain abrasive performance characteristics(e.g., cut rate, surface finish, abrasive grain retention, mechanicalstress resistance, thermal resistance, and solvent resistance) underdemanding conditions (e.g., high-speed abrading and grinding),conventional abrasive articles typically incorporate components, such aspolymer binder systems, abrasive grains, and backing materials thatcontain environmentally harmful chemicals or are themselvesenvironmentally unfriendly due to a lack of biodegradability,recyclability, or re-usability.

For instance, phenol-formaldehyde resins (i.e., novolac and resoleresins) and urea-formaldehyde resins are commonly encountered asabrasive binder compositions in conventional abrasive articles. At leastone drawback of these phenol-formaldehyde and urea-formaldehyde resinsis that they contain formaldehyde, which can be harmful to people andthe environment.

Although various efforts have been made to replace various components ofabrasive articles, there continues to be a demand for improved, costeffective, abrasive articles, processes, and systems that can promoteand achieve efficient abrasion and improved surface characteristics, butthat are at the same time environmentally friendly.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerousfeatures and advantages made apparent to those skilled in the art byreferencing the accompanying drawings.

FIG. 1 is an illustration of a cross-section of a coated abrasiveembodiment according to the present invention.

FIG. 2 is an illustration of a cross-section of another coated abrasiveembodiment according to the present invention.

FIG. 3 is an illustration of a flowchart of a method of making a coatedabrasive according to the present invention.

FIG. 4 is an illustration of a flowchart of another method making acoated abrasive according to the present invention.

The use of the same reference symbols in different drawings indicatessimilar or identical items.

DETAILED DESCRIPTION

The present inventors have surprisingly discovered abrasive articleembodiments that achieve or exceed the performance characteristics ofcertain conventional abrasive articles, but that do not rely onphenol-formaldehyde or urea-formaldehyde binder compositions.Embodiments described in greater detail below comprise an aqueous resincomposition adapted to be used as a binder of abrasive particles and areformaldehyde-free.

Illustrated in FIG. 1 is an embodiment of a coated abrasive article 100,commonly called a “coated abrasive.” The coated abrasive 100 includes abacking 101 and an abrasive layer 103 disposed on the backing 101. Theabrasive layer 103 comprises a plurality of abrasive particles 105 thatare retained by a polymer binder composition 107. The polymer bindercomposition 107 is commonly called a “make coat” where the abrasiveparticles 105 are disposed on the surface 109 of the polymer bindercomposition and are partially embedded in the polymer bindercomposition. The coated abrasive 100 can also include a size coat 111overlying the abrasive layer 103. Optionally, a supersize coat (notillustrated) can be overlying the size coat 111. Further, an adhesionpromoting layer (not illustrated) can optionally be located between thebacking 101 and the abrasive layer 103.

Illustrated in FIG. 2 is another embodiment of a coated abrasive article200. The coated abrasive 200 includes a backing 201 and an abrasivelayer 203 disposed on the backing 201. The abrasive layer 203 comprisesa plurality of abrasive particles 205 dispersed within a polymer bindercomposition 207. The abrasive layer 203 is commonly called an “abrasiveslurry coat” where the abrasive particles 205 are dispersed within thepolymer binder composition 207. The coated abrasive 200 can also includea size coat 209 overlying the abrasive layer 203. Optionally, asupersize coat (not illustrated) can be overlying the size coat 209.Further, an adhesion promoting layer (not illustrated) can optionally belocated between the backing 201 and the abrasive layer 203.

Illustrated in FIG. 3 is an embodiment of a process 300 for preparing acoated abrasive article. In step 301, forming a polymer bindercomposition occurs by mixing together a saccharide, a polycarboxylicorganic acid, and a crosslinking catalyst. In step 303, providing abacking occurs. In step 305, forming a make coat occurs by disposing thepolymer binder composition overlying the backing. Applying abrasiveparticles to the make coat occurs in step 307. Curing of the make coatoccurs in step 309. The curing in step 309 can be partial curing of themake coat or full curing of the make coat. In an optional step 311, asize coat can be disposed overlying the make coat. Curing of the sizecoat can occur in step 313. The curing in step 313 can be partial curingof the size coat or full curing of the size coat. In optional step 315,a supersize coat can be disposed overlying the size coat. Curing of thesupersize coat can occur in step 317. The curing in step 317 can bepartial curing of the supersize coat or full curing of the supersizecoat.

Illustrated in FIG. 4 is an embodiment of a process 400 for preparing acoated abrasive article. In step 401, mixing together of polymer bindercomposition of a saccharide, a polycarboxylic organic acid, and acrosslinking catalyst and abrasive particles occurs to form an abrasiveslurry composition. In step 403, providing a backing occurs. Applyingthe abrasive slurry composition to the backing occurs in step 405.Curing of the abrasive slurry composition occurs in step 407. The curingin step 407 can be partial curing of the abrasive slurry composition orfull curing of the abrasive slurry composition. In an optional step 409,a size coat can be disposed overlying the abrasive slurry composition.Curing of the size coat can occur in step 411. The curing in step 411can be partial curing of the size coat or full curing of the size coat.In optional step 413, a supersize coat can be disposed overlying thesize coat. Curing of the supersize coat can occur in step 415. Thecuring in step 415 can be partial curing of the supersize coat or fullcuring of the supersize coat.

Abrasive Layer

An abrasive layer can comprise a make coat or an abrasive slurry. Themake coat or abrasive slurry can comprise a plurality of abrasiveparticles, also referred to herein as abrasive grains, retained by apolymer binder composition. The polymer binder composition can be anaqueous composition. The polymer binder composition can be athermosetting composition. The polymer binder composition can be athermosetting composition. In an embodiment, the polymer bindercomposition is an aqueous thermosetting composition comprising comprisesat least one saccharide, at least one polycarboxylic organic acid and atleast one crosslinking catalyst.

Saccharides

The present embodiments comprise at least one saccharide. The at leastone saccharide can include saccharides that are the same or aredifferent. In an embodiment, the at least one saccharide can be amonosaccharide, monosaccharides, an oligosaccharide, oligosaccharides, apolysaccharide, polysaccharides, or combinations thereof.

A monosaccharide can have 3 to 8 carbon atoms. In an embodiment, amonosaccharide can be an aldose having 5 to 7 carbon atoms. In anotherembodiment, a monosaccharide can be a hexose. In a particularembodiment, a hexose can be glucose, mannose, galactose, or combinationsthereof.

A polysaccharide has a number-average molecular weight of less than5000. In an embodiment, a polysaccharide can have a polydispersity index(IP), defined as the ratio of the weight-average molecular weight of thepolysaccharide to the number-average molecular weight of thepolysaccharide that is less than or equal to 12. In an embodiment, apolysaccharide comprises at least two saccharide units. The at least twosaccharide units can be the same or different. In an embodiment the atleast two saccharide units can be aldoses. In a specific embodiment theat least two saccharide units are glucose. In a particular embodiment, apolysaccharide is predominantly (more than 50% by weight) glucose units.

In another embodiment, the at least one saccharide can be a mixture ofmonosaccharides, oligosaccharides, polysaccharides, or combinationsthereof that are obtained from plants. In a particular embodiment, theat least one saccharide is corn syrup. Corn syrup is a liquid mixture ofpartially hydrolyzed starch comprised of oligosaccharides, maltose, anddextrose.

In another embodiment, the at least one saccharide is a dextrin orcombination of dextrins. Dextrins are compounds corresponding to thegeneral formula (C6H10O5)n, usually obtained by partial hydrolysis ofstarch. In a particular embodiment, the dextrin is a solid low molecularweight crystalline polysaccharide.

Polycarboxylic Organic Acids

The polymer binder composition can also in include one or morepolycarboxylic organic acids. The expression “polycarboxylic organicacid” as used herein is meant to encompass an organic acid comprising atleast two carboxylic functions and at most 1000 carboxylic functions. Ina specific embodiment, a polycarboxylic organic acid can have two to 500carboxylic functions. Polycarboxylic organic acids are capable ofreacting with hydroxyl groups of the saccharide under the effect of heatto form ester bonds that result in a polymer network being obtained inthe final binder. Said polymer network makes it possible to establishbonds at the points of contact with the abrasive particles.Polycarboxylic organic acids can be the same or different. Thepolycarboxylic organic acid can be a monomeric or polymericpolycarboxylic organic acid.

In an embodiment, the polycarboxylic organic acid can be a monomericpolycarboxylic organic acid or a dicarboxylic acid. Dicarboxylic acidsinclude oxalic acid, malonic acid, succinic acid, glutaric acid, adipicacid, pimelic acid, suberic acid, azelaic acid, sebacic acid, malicacid, tartaric acid, tartronic acid, aspartic acid, glutamic acid,fumaric acid, itaconic acid, maleic acid, traumatic acid, camphoricacid, phthalic acid and its derivatives, especially containing at leastone boron or chlorine atom, tetrahydrophthalic acid and its derivatives,especially containing at least one chlorine atom such as chlorendicacid, isophthalic acid, terephthalic acid, mesaconic acid, citraconicacid and 2,5-furanedicarboxylic acid; tricarboxylic acids, such ascitric acid, tricarballylic acid, 1,2,4-butanetricarboxylic acid,aconitic acid, hemimellitic acid, trimellitic acid and trimesic acid;tetracarboxylic acids, such as 1,2,3,4-butanetetracarboxylic acid andpyromellitic acid, and mixtures of these acids. In a specificembodiment, the polycarboxylic organic acid is citric acid.

Polymeric polycarboxylic organic acids also includes homopolymers of anunsaturated carboxylic organic acid such as (meth)acrylic acid, crotonicacid, isocrotonic acid, maleic acid, cinnamic acid, 2-methylmaleic acid,fumaric acid, itaconic acid, 2-methylitaconic acid,α,β-methyleneglutaric acid and unsaturated dicarboxylic acid monoesters,such as C1-C10 alkyl maleates and fumarates, and copolymers of at leastone aforementioned unsaturated carboxylic acid and of at least one vinylmonomer, such as styrene, which may or may not be substituted by alkyl,hydroxyl or sulphonyl groups, or may be substituted by a halogen atom,(meth)acrylonitrile, (meth)acrylamide, or may not be substituted byC1-C10 alkyl groups, alkyl(meth)acrylates, especiallymethyl(meth)acrylate, ethyl(meth)acrylate, n-butyl(meth)acrylate andisobutyl(meth)acrylate, glycidyl(meth)acrylate, butadiene and a vinylester, especially vinyl acetate.

In an embodiment, the polymer binder composition contains at least onepolymeric polycarboxylic organic acid. In another embodiment, thepolymer binder composition contains at least one polymer or onecopolymer of (meth)acrylic acid. In a specific embodiment, the at leastone polymer or one copolymer of (meth)acrylic acid is in a mixture withcitric acid.

Cross-Linking Catalyst

The polymer binder composition comprises at least at least onecrosslinking catalyst. The crosslinking catalyst functions to adjust thecrosslinking start temperature of the saccharide with the polycarboxylicorganic acid.

The crosslinking catalyst is chosen from compounds that containphosphorus, such as an alkali metal hypophosphite salt, an alkali metalphosphite, an alkali metal polyphosphate, an alkali metalhydrogenphosphate, a phosphoric acid or an alkylphosphonic acid.Preferably, the alkali metal is sodium or potassium.

The crosslinking catalyst may also be chosen from Lewis acids and bases,such as clays, colloidal or non-colloidal silica, organic amines,quaternary amines, metal oxides, metal sulphates, metal chlorides, ureasulphates, urea chlorides and silicate-based catalysts.

The catalyst may also be a compound that contains fluorine and boron,for example tetrafluoroboric acid or a salt of this acid, especially atetrafluoroborate of an alkali metal, such as sodium or potassium, atetrafluoroborate of an alkaline-earth metal, such as calcium ormagnesium, a zinc tetrafluoroborate and an ammonium tetrafluoroborate.

In an embodiment, the crosslinking catalyst is sodium hypophosphite,sodium phosphite, and mixtures of these compounds.

Rheology Modifiers

The polymer binder composition can include one or more rheologymodifiers. A rheology modifier can be used to influence the viscosity ofthe polymer binder composition and thus influence the orientation ofabrasive particles applied to a make coat. In an embodiment, a rheologymodifier can be a single type of rheology modifier or a mixture ofrheology modifiers. In an embodiment, a rheology modifier can be derivedfrom environmentally sustainable materials. In a specific embodiment, arheology modifier can be starch, Bentonite clay, ethyl cellulose, methylcellulose, fumed silica, a polysaccharide based gum, or combinationsthereof. In a specific embodiment, a rheology modifier can be pectin,xanthan gum, gum Arabic, or combinations thereof. In a particularembodiment, a rheology modifier is Xanthan gum. A rheology modifier canbe activated by exposure to heat prior to use.

Fillers

The polymer binder composition can include one or more fillers. Thefiller can be a single type of filler or a mixture of fillers. Thefiller can serve to increase the Young's modulus of the polymer bindercomposition. The filler can serve to modify the pH of the polymer bindercomposition. Suitable fillers can be synthetic materials or naturallyoccurring materials. A filler can be an inorganic or organic material.In an embodiment, the filler is derived from an environmentallysustainable material. Suitable inorganic fillers can include calciumsulfate (gypsum). Suitable organic fillers can include hard materialsthat are biodegradable. In an embodiment, an organic filler can includeground nut shells.

Hydrophobic Additives/Hydrophobizing Agents

The polymer binder composition can include one or more hydrophobicadditives, also called hydrophobizing agents herein they impart improvedwater resistance. The hydrophobic additives can be a single type ofhydrophobic additive or a mixture of hydrophobic additives. Thehydrophobic additives can serve to reduce water absorption and preservemechanical strength. Further, hydrophobic additives can reduce surfacetackiness, thus avoiding blocking problems during production of rolledcoated abrasive product, as well as avoiding excessive swarf pick upduring sanding operations. Moreover, because steam is commonly usedduring the production of coated abrasives to mitigate edge curl,degradation of a coated abrasive's size coat and/or make coat can beavoided by the inclusion of hydrophobic additives. Suitable hydrophobicadditives can be synthetic materials or naturally occurring materials. Ahydrophobic additive can be an inorganic or organic material. In anembodiment, the hydrophobic additive is derived from an environmentallysustainable material. Suitable organic hydrophobic additives can includematerials that are biodegradable. In an embodiment, an organichydrophobic additive can be tall oil fatty acid dimer emulsions, abieticacid salts, tree rosin soaps, vegetable based waxes, levulinic acid, andcombinations thereof. In a specific embodiment, a hydrophobic additiveis a vegetable based wax, such as a sunflower wax, rice bran wax, orcombinations thereof.

Other Additives

The aqueous resin composition may also comprise other additives that aidthe manufacture of an abrasive article. Other additives can includeclays; such as kaolin; salts, pH modifiers, adhesion promoters,thickeners, plasticizers, lubricants, bactericides, fungicides, wettingagents, antistatic agents, pigments, dyes, coupling agents; such asalkoxysilanes; flame retardants, degassing agents, anti-dusting agents,thixotropic agents, dual function materials, initiators, surfactants,chain transfer agents, stabilizers, dispersants, reaction mediators,pigments, dyes, colorants, and defoamers.

Abrasive Particles

A plurality of abrasive particles can be applied to the polymer bindercomposition. The term abrasive particles, as used herein alsoencompasses abrasive grains, abrasive agglomerates, abrasive aggregates,green-unfired abrasive aggregates, shaped abrasive particles, andcombinations thereof. As described previously, the plurality of abrasiveparticles can be applied to a make coat of the polymer bindercomposition, or be dispersed in a slurry coat of the polymer bindercomposition. Thus, the abrasive particles can be disposed on the polymerbinder composition, be at least partially embedded in the polymer bindercomposition, or a combination thereof. The abrasive particles cangenerally have a Mohs hardness of greater than about 3, and preferablyin a range from about 3 to about 10. For particular applications, theabrasive particles can have a Mohs hardness of at least 5, 6, 7, 8, or9. In an embodiment, the abrasive particles have a Mohs hardness of 9.Suitable abrasive particles include non-metallic, inorganic solids suchas carbides, oxides, nitrides and certain carbonaceous materials. Oxidescan include silicon oxide (such as quartz, cristobalite and glassyforms), cerium oxide, zirconium oxide, and various forms of aluminumoxide (including fused aluminas, sintered aluminas, seeded andnon-seeded sol-gel aluminas). Carbides and nitrides can include siliconcarbide, aluminum carbide, aluminum nitride, aluminum oxynitride, boronnitride (including cubic boron nitride), titanium carbide, titaniumnitride, and silicon nitride. Carbonaceous materials can includediamond, which broadly includes synthetic diamond, diamond-like carbon,and related carbonaceous materials such as fullerite and aggregatediamond nanorods. Suitable abrasive particles can also include a widerange of naturally occurring mined minerals, such as garnet,cristobalite, quartz, corundum, and feldspar. In particular embodiments,the abrasive particles can be diamond, silicon carbide, aluminum oxide,cerium oxide, or combinations thereof. Abrasive particles can bemixtures of two or more different abrasive particles or can be a singletype of abrasive particle.

In a particular embodiment, the abrasive particles are derived from anenvironmentally sustainable material, a recyclable material, or areusable material. In an embodiment, the abrasive particles are recycledabrasive particles. In a specific embodiment, the abrasive particles arerecycled aluminum oxide particles.

Backing

In accordance with an embodiment, the backing can be an organicmaterial, inorganic material, natural material, synthetic material, orcombinations thereof. The backing can be flexible or rigid and can bemade of a single material or combination of various materials. Aparticular flexible backing includes a polymeric film (for example, aprimed film), such as polyolefin film (e.g., polypropylene includingbiaxially oriented polypropylene), polyester film (e.g., polyethyleneterephthalate), polyamide film, or cellulose ester film; metal foil;mesh; foam (e.g., natural sponge material or polyurethane foam); cloth(e.g., cloth made from fibers or yarns comprising polyester, nylon,silk, cotton, poly-cotton, or rayon); paper; vulcanized paper;vulcanized rubber; vulcanized fiber; nonwoven materials; any combinationthereof; or any treated version thereof. Cloth backings can be woven orstitch bonded. In a particular embodiment, the backing includes athermoplastic film, such as a polyethylene terephthalate (PET) film. Inparticular, the backing can be a single layer polymer film, such as asingle layer PET film. In particular embodiment, the backing is aflexible support material, sheet of paper, a film or a network offibers, for example a mat, a felt, a fabric or a knit of natural orsynthetic fibers, including mineral fibers, glass fibers, polymerfibers, plant fibers, or combinations thereof.

In a particular embodiment, the backing material is derived from anenvironmentally sustainable material, a recyclable material, or areusable material. In a particular embodiment, the backing material is arecycled paper backing. In another particular embodiment, the backingmaterial is a paper backing derived from plant material that originatesfrom a well-managed forest, such as a Forest Stewardship Council managedforest, a controlled source of natural and recycled wood, natural andrecycled plant fibers, and combinations thereof.

Size Coat

The coated abrasive article can comprise a size coat overlying theabrasive layer. The size coat can be the same as or different from thepolymer binder composition used to form the abrasive layer. The sizecoat can comprise any conventional compositions known in the art thatcan be used as a size coat. In an embodiment, the size coat comprises aconventionally known composition overlying the polymer bindercomposition of the abrasive layer. In another embodiment, the size coatcomprises the same ingredients as the polymer binder composition of theabrasive layer. In a specific embodiment, the size coat comprises thesame ingredients as the polymer binder composition of the abrasive layerand one or more hydrophobic additives. In a specific embodiment, thehydrophobic additive can be a wax, a halogenated organic compound, ahalogen salt, a metal, or a metal alloy.

Supersize Coat

The coated abrasive article can comprise a supersize coat overlying thesize coat. The supersize coat can be the same as or different from thepolymer binder composition or the size coat composition. The supersizecoat can comprise any conventional compositions known in the art thatcan be used as a supersize coat. In an embodiment, the supersize coatcomprises a conventionally known composition overlying the size coatcomposition. In another embodiment, the supersize coat comprises thesame ingredients as at least one of the size coat composition or thepolymer binder composition of the abrasive layer. In a specificembodiment, the supersize coat comprises the same composition as thepolymer binder composition of the abrasive layer or the composition ofthe size coat plus one or more grinding aids.

Suitable grinding aids can be inorganic based; such as halide salts, forexample sodium cryolite, and potassium tetrafluoroborate; or organicbased, such as sodium lauryl sulphate, or chlorinated waxes, such aspolyvinyl chloride. In an embodiment, the grinding aid can be anenvironmentally sustainable material.

Coated Abrasive Article Preparation Polymer Binder Preparation

As shown in FIG. 3 an embodiment of a process 300 for preparing a coatedabrasive article is given. At step 301, forming a polymer bindercomposition can be accomplished by mixing together a saccharide, apolycarboxylic organic acid, and a crosslinking catalyst in the presenceof water. The saccharide, a polycarboxylic organic acid, crosslinkingcatalyst, and water are combined together until thoroughly mixed. Thepolymer binder composition can additionally comprise other ingredients,such as rheology modifiers, fillers, hydrophobic additives, and otheradditives.

All the mixture ingredients are thoroughly mixed together using, forexample, a high shear mixer. Mixing can be conducted using high shearconditions, medium shear conditions, or low shear conditions, asdesired. Typically, mixing occurs until the ingredients are thoroughlymixed. During mixing of the ingredients, the ingredients may be added tothe mixture one by one, in batches, or all at once.

The viscosity of the polymer binder mixture can be monitored as it isbeing prepared. In an embodiment, the viscosity of the polymer bindermixture can be kept in a particular range by the addition of rheologymodifiers, thickeners, plasticizers, diluents, thixotropic agents, orcombinations thereof. In the event of the addition of any solidcomponents, such as abrasive particles during abrasive slurrypreparation, the mixture can have a viscosity adjusted in a particularrange.

The pH of the aqueous polymer binder composition is generally acidic. Inan embodiment, the pH is in a range from 1 to 5. In a specificembodiment, the pH is greater than or equal to 1.5. The pH can varydepending on the nature of the polycarboxylic organic acid used. In anembodiment the pH is maintained at a value at least equal to 2. A pH ofat least equal to 2 can limit instability problems of the aqueous resincomposition. The pH can be adjusted by the addition of an acid or otherpH modifier.

The viscosity of the aqueous polymer binder composition can varydepending on the desired application conditions but will generallyremain less than or equal to 15,000 mPa·s, preferably less than or equalto 10,000 mPa·s, measured at 25° C. using a Brookfield machine fittedwith an LV1 spindle operating at a speed of 60 rpm.

In an embodiment, the polycarboxylic organic acid comprises a mixture ofmonomeric polycarboxylic organic acid and polycarboxylic acid. Inanother embodiment, the amount by weight of monomeric polycarboxylicorganic acid ranges from 5 to 50%, such as from 15 to 40%, of the totalweight of monomeric polycarboxylic organic acid and polymericpolycarboxylic organic acid.

In the aqueous resin composition, the amount, by weight, of sacchariderepresents 10% to 90%, such as 40% to 70%, of the total weight of thesaccharide and polycarboxylic organic acid.

The amount of catalyst introduced into the aqueous resin compositionrepresents 1% to 15%, such as 3% to 10%, of the total weight of thesaccharide and polycarboxylic organic acid.

The solids content of the aqueous polymer binder composition can becalculated. In an embodiment, the solids content can be calculated onthe basis of all the organic constituents. In a specific embodiment, thesolids content can be in a range from 30% to 75%, preferably from 45% to70%.

In step 305, a make coat can be formed by disposing the polymer bindercomposition onto a backing. The polymer binder composition can be coatedonto the backing using a blade spreader to form a make coat.Alternatively, the polymer binder composition can be applied using slotdie, smooth rolling, gravure, or reverse gravure coating methods.

Abrasive particles can be applied to the make coat in step 307 throughelectrostatic attraction (sometimes called “upcoating”) or simply downthrough gravity (e.g., sprinkled onto the backing). Both approaches arewell understood in the art, generally first depositing a ‘make coat’ onthe backing, followed by abrasive aggregate application onto the makecoat, and subsequent deposition of a ‘size coat’ in step 311.

Optionally, a supersize coat may be deposited over the size coat as instep 313. Deposition of the supersize coat can be accomplished by thesame methods as for the make coat and size coat.

In sum, the aqueous polymer binder composition can be used to form themake coat, the size coat or the supersize coat. Preferably, the aqueouscomposition is used to form the size coat, and where appropriate themake coat.

Applying an Abrasive Slurry to a Backing

As shown in FIG. 4, in an alternative method 400, an abrasive slurrycontaining the polymer binder composition and abrasive particles ismixed together. The aqueous polymer binder composition can be mixed asdescribed above with the addition that a desired amount of abrasiveparticles are added in during the mixing process to form an abrasiveslurry. The abrasive slurry is preferably applied to the backing using ablade spreader. Alternatively, the slurry coating can be applied usingslot die, smooth rolling, gravure, or reverse gravure coating methods.

Curing the make Coat, Abrasive Slurry, Size Coat, and Supersize Coat

The coated backing is then heated in order to cure the polymer bindercomposition and bond the abrasive particles (aggregates, grains, orcombination thereof) to the backing. The polymer binder composition;whether in the form of a make coat, abrasive slurry, size coat, orsupersize coat; can be at least partially cured or fully cured.Additional molding or shaping of a partially cured coating can beperformed prior to full curing, if desired. Said molding and shaping canbe performed on an abrasive slurry so that an engineered abrasivearticle, also called a structured abrasive article, is formed. Fullcuring completes crosslinking of the constituents contained in a coat.In general, the coated backing is heated to a temperature in a range ofabout 100° C. to less than about 250° C. during the curing process. Incertain embodiments the curing step can be carried out at a temperatureof less than about 200° C. In an embodiment, the application of eachmake coat or supersize coat is followed by a heat treatment at atemperature of less than or equal to 150° C., preferably less than orequal to 120° C., and advantageously between 50° C. and 100° C. The heattreatment can last from 1 to 120 minutes, preferably 1 to 90 minutes.

Once the resin is fully cured, the abrasive aggregates are bonded to thebacking and the coated backing may be used for a variety of stockremoval, finishing, and polishing applications.

The coated abrasive obtained may be cut to the desired size, for exampleto produce sheets, or collected in the form of a winding.

The winding may undergo an additional heat treatment with a view tocompleting the crosslinking of the aqueous composition forming the sizecoat or the supersize coat. This heat treatment may be carried out at atemperature less than or equal to 150° C., preferably less than or equalto 120° C., for at most 36 hours, preferably at most 20 hours.

Coated abrasive articles incorporating the aqueous polymer bindercomposition according to the embodiments can be, in particular, in theform of abrasive papers and abrasive fabrics.

The examples given below make it possible to illustrate the inventionwithout however limiting it.

In the examples, the viscosity (in mPa·s) is measured at 25° C. using aBrookfield machine equipped with an LV1 spindle rotating at a speed of60 rpm. The viscosity is measured immediately after the manufacture ofthe aqueous resin composition and after storing for one day at 25° C.

In the examples, the Young's modulus is measured by the nanoindentationtechnique which makes it possible to evaluate the mechanical propertiesof a thin film deposited on a substrate, without these properties beinginfluenced by the substrate. The Young's modulus is measured under thefollowing conditions: a layer of aqueous resin composition (thickness:150 μm) is deposited on a square glass plate having 1 cm sides, and theassembly is heated at 60° C. for 60 minutes, then at 120° C. for 120minutes. The glass plate is placed in a nanoindenter (XP sold by MTSSystems Corp.) equipped with a diamond Berkovich tip of triangular-basedpyramid shape, and the curve of the load as a function of thedisplacement is established. The Young's modulus, in GPa, is determinedfrom this curve. The value of the Young's modulus is an average of 10measurement points.

In the examples, the loss of mass is determined by thermogravimetricanalysis (TGA). The aqueous resin composition is deposited in analuminium pan and heated at 60° C. for 60 minutes, then at 120° C. for120 minutes. 10 to 20 mg of the residue obtained (binder) are placed inan alumina crucible which is put into a machine that continuouslymeasures the loss of mass during a temperature cycle ranging from 25° C.to 700° C. at a rate of 10° C./minute. The loss of mass at 300° C., 400°C. and 500° C. is determined from the recorded curve.

EXAMPLES 1 TO 8

Aqueous resin compositions are manufactured by mixing in a container,with stirring, the compounds that appear in Table 1, the amounts beingexpressed in parts by weight. The solids content of these compositionsis between 50% and 60% and their viscosity appears in Table 1.

The loss of mass (see Table 1) is measured in parallel on a portion ofthe resin compositions.

Each of the aqueous resin compositions obtained and also a conventionalcomposition based on a urea-formaldehyde resin, denoted by Reference(sold under the reference R2130 by the company SchenectadyInternational, Inc.) are applied in the form of a film (thickness 150μm) to a glass plate.

The glass plate is introduced into an oven and brought to a temperatureof 60° C. for 60 minutes, then 120° C. for 120 minutes. The propertiesindicated in Table 1 are measured on the cooled plate.

The viscosity of the resin compositions of Examples 1 to 8 is compatiblewith a use to produce coated abrasive articles.

The Young's modulus of the examples according to the invention is higherthan that of the Reference.

The loss of mass of Examples 1 to 8 remains lower than that of theReference, irrespective of the measurement temperature. Examples 1 to 5,which contain a polymeric polycarboxylic organic acid, have the lowestloss of mass.

EXAMPLES 9 AND 10

These examples illustrate the preparation of a coated abrasive articleon a pilot line.

From a reel, a sheet of paper (ARJOREG-185-MS-WHITE sold by ARJOWIGGINS; width: 30 cm; basis weight: 185 g/m²; thickness 0.21 mm) isunwound and a make coat is deposited, continuously, using a transferroll, then abrasive particles are deposited using an electrostaticcoating device. The coated sheet is collected in the form of festoons ona suitable device which is then introduced into an oven at 85° C. for 20minutes.

After cooling, the sheet is again wound in the form of a reel which isplaced in the preceding unit in order to deposit the size coat on theface bearing the abrasive particles. The sheet is collected and treatedunder the following temperature conditions: 85° C. for 50 minutes(Example 9) and 50° C. for 50 minutes (Example 10).

The sheet of Example 9 is again wound in the form of a reel andintroduced into an oven at 115° C. for 120 minutes.

The make coat is constituted of the urea-formaldehyde (Reference) resindescribed in Examples 1 to 8, to which 10 parts by weight of kaolin havebeen added. The make coat is deposited in a proportion of 52 g/m² (dryweight).

The abrasive particles are constituted of alumina (sold under thereference “Electrocorundum EKP, P80 grit” by the company KuhmichelAbrasiv GmbH) and are deposited in a proportion of 165 g/m².

The size coat is constituted of the aqueous resin composition of Example5 (Example 9) or of the aforementioned Reference resin (comparativeExample 10). The size coat is deposited in a proportion of 120 g/m² (dryweight).

The performances of the abrasive sheet are evaluated under theconditions of the following abrasion test: discs with a diameter of 125mm bearing 8 holes of 8 mm are cut from the abrasive sheet and one discis placed on an electric sander (Bosch PEX 220A). The sander is used byan operator to manually sand a sheet of wood made of pine (length: 80cm; width: 20 cm; thickness: 1.5 cm) with a linear movement in thelength direction.

The loss of mass of the sheet of wood as a function of the sanding timeis measured. The results are given in Table 2, expressed as cumulativeloss of mass.

Example 9 has abrasive properties equivalent to those of comparativeExample 10.

TABLE 1 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 ReferenceAqueous resin composition Acusol 445⁽¹⁾ 40 40 40 25 25 — — — — Citricacid — — — 15 15 40 40 40 — Sodium hypophosphite 5 5 5 5 5 5 5 5 —Glucidex ® 12⁽²⁾ 60 — — — — 60 — — — Glucidex ® 19 D⁽³⁾ — 60 — 60 — — 60— — Tackidex ® C172⁽⁴⁾ — — 60 — — — — 60 — Roclys ® 3072S⁽⁵⁾ — — — — 60— — — — Properties Viscosity (mPa · s) Initial 1230 220 4400 1500 1000110 80 120 1000 1 day 4570 1560 5400 1880 1430 200 100 170 1100 Young'smodulus (GPa) 17.0 15.2 16.5 15.5 n.d. n.d. n.d. n.d. 8.5 Loss of mass(%) 300° C. 25 25 25 25 23 44 42 42 60 400° C. 50 50 51 50 45 66 65 6675 500° C. 60 59 61 61 55 74 76 75 80 n.d.: not determined ⁽¹⁾acrylicacid homopolymer; sold by Dow Chemicals ⁽²⁾maltodextrin; number-averagemolecular weight: 1725 g/mol; polydispersity index (IP): 10.6; sold byRoquette ⁽³⁾dextrin; number-average molecular weight: 1165 g/mol;polydispersity index (IP): 8.6; sold by Roquette ⁽⁴⁾maltodextrin;number-average molecular weight: 2490 g/mol; polydispersity index (IP):5.2; sold by Roquette ⁽⁵⁾glucose syrup; number-average molecular weight:675 g/mol; polydispersity index (IP): 5.4; sold by Roquette

TABLE 2 Abrasion test Ex. 10 Cumulative loss of mass (g) Ex. 9(comparative)  2 minutes 4.6 4.8  4 minutes 8.1 6.6  6 minutes 11.7 12.2 8 minutes 14.9 15.4 10 minutes 17.9 18.8 12 minutes 20.9 21.9 14minutes 23.7 24.8 17 minutes 26.3 28.5 20 minutes 29.8 32.0 23 minutes33.7 35.1 26 minutes 37.2 38.3 30 minutes 41.2 42.0

1. A coated abrasive article comprising: a backing; and an abrasivelayer overlying the backing; wherein the abrasive layer comprisesabrasive particles and a polymer binder composition including at leastone saccharide, at least one polycarboxylic organic acid, and at leastone crosslinking catalyst.
 2. A coated abrasive article comprising: abacking; and an abrasive layer overlying the backing; and a size coatcomprising a polymer binder composition including at least onesaccharide, at least one polycarboxylic organic acid, and at least onecrosslinking catalyst.
 3. A coated abrasive article according to claim 1wherein the saccharide is corn syrup, dextrin, or a combination thereof.4. A coated abrasive article according to claim 1 wherein the polymerbinder further comprises at least one member selected from the groupconsisting of rheology modifiers and hydrophobic additives. 5.(canceled)
 6. A coated abrasive article according to claim 1, whereinthe saccharide is a monosaccharide, a polysaccharide, or a combinationthereof.
 7. (canceled)
 8. A coated abrasive article according to claim1, wherein the saccharide comprises is glucose, mannose or galactose. 9.A coated abrasive article according to claim 6, wherein thepolysaccharide has a number-average molecular weight of less than 5000.10. A coated abrasive article according to claim 9, wherein thepolysaccharide has a polydispersity index (IP), defined by the ratio ofthe weight-average molecular weight to the number-average molecularweight, which is less than or equal to
 12. 11. (canceled)
 12. (canceled)13. A coated abrasive article according to claim 1, further comprising amonomeric polycarboxylic organic acid.
 14. A coated abrasive articleaccording to claim 13, wherein the monomeric polycarboxylic acid iscitric acid.
 15. A coated abrasive article according to claim 1, whereinthe polymeric polycarboxylic organic acid is chosen from homopolymers ofan unsaturated carboxylic organic acid and unsaturated dicarboxylic acidmonoesters, and copolymers of at least one aforementioned unsaturatedcarboxylic acid and of at least one vinyl monomer.
 16. A coated abrasivearticle according to claim 1, wherein the polymeric polycarboxylicorganic acid contains at least one polymer or one copolymer of(meth)acrylic acid.
 17. A coated abrasive article according to claim 1,wherein the amount, by weight, of saccharide represents 10% to 90% ofthe total weight of the saccharide and polycarboxylic organic acid. 18.A coated abrasive article according to claim 1, wherein the crosslinkingcatalyst is chosen from compound salts that contain phosphorus, Lewisacids and bases, organic amines, metal oxides, metal sulphates, metalchlorides, urea sulphates, urea chlorides and silicate-based catalystsand compounds that contain fluorine and boron.
 19. A coated abrasivearticle according to claim 18, wherein the crosslinking catalyst issodium hypophosphite, sodium phosphite, or a combination thereof.
 20. Acoated abrasive article according to one claim 1, wherein the amount ofcrosslinking catalyst represents 1% to 15% of the total weight of thesaccharide and polycarboxylic organic acid.
 21. A coated abrasivearticle according to claim 1, wherein the solids content, calculated onthe basis of all of the organic constituents, varies from 30% to 75%.